In the conventional combustion means for a solid fuel, there is provided, in the combustion chamber, a roaster comprising a plane board in the center of which a number of air slits are formed at a fixed position. In case of burning the solid fuel, the solid fuel is piled up in a fixed height on the roaster and the piled fuel is ignited by an appropriate igniting means and is continuously burnt (cf. Japanese Utility Model Publication Nos. 36174/1964, 36175/1974 and 23003/1975). In this burning process, the solid fuel to be used is required to have fire-durability for a long time for the purpose of its use. On burning, when the solid fuel having an ash content of not more than 10% is used, it falls down from the space of the roaster, which results in lowering of heat efficiency. For preventing this drawback, when the solid fuel having an ash content of not less than 10% is used, it remains as the ash having an original shape of the solid fuel even after burning, without falling down from the roaster so that the heat efficiency can be kept for a long time. In this case, however, the amount of the ash which has remained after burning is increased and requires much effort for removing it, and further the selection of the starting material for the fuel and the molding of the same cause higher cost. For overcoming the above drawbacks, the use of solid fuel having low ash content has been proposed, whereby there is little fear of contaminating the air and the problem relating to the removal of the remaining ash in the combustion apparatus can be solved.